U.S. historian and civil rights advocate John Hope Franklin, credited with helping create the field of African-American history, died on Wednesday at age 94, Duke University said.

He worked with Thurgood Marshall, later the first black U.S. Supreme Court justice, on the landmark Brown v. Board of Education case in the 1950s in which the Supreme Court declared segregation in public schools unconstitutional.

Franklin joined civil rights protesters in a 1965 march for voting rights led by the Rev. Martin Luther King Jr. in Montgomery, Alabama. In 1997, he was appointed chairman of President Bill Clinton's One America Initiative, charged with directing a national conversation on race relations.

"Because of the life John Hope Franklin lived, the public service he rendered, and the scholarship that was the mark of his distinguished career, we all have a richer understanding of who we are as Americans and our journey as a people," President Barack Obama said in a statement. Obama is America's first black president.

The grandson of a slave, Franklin's scholarly work was informed by his first-hand experience with racism.

In a speech in 2005, he said that on the evening before he received the Presidential Medal of Freedom from Clinton in 1995, a woman at his club in Washington asked him to get her coat. About the same time, a man at a hotel handed his car keys to Franklin and told him to get his car.

"I patiently explained to him that I was a guest in the hotel, as I presumed he was, and I had no idea where his automobile was. And, in any case, I was retired," Franklin said.